In the prior-art anesthetic vaporizer, the gas flow is split into a bypass gas flow and an evaporator chamber gas flow after a gas inlet opening. The bypass gas flow flows via a bypass resistance to the outlet. The evaporator chamber gas flow is sent through an evaporator chamber, which is partly filled with liquid anesthetic, and is concentrated there to saturation while flowing past the surface of the anesthetic. Via a dispensing element, which is arranged downstream of the evaporator chamber, the evaporator chamber gas flow is again united with the bypass gas flow at a mixing site. The anesthetic concentration obtained at the mixing site or the gas discharge opening is obtained from the split ratio of the bypass gas flow to the evaporator chamber gas flow. The quantity of anesthetic vapor that is mixed with the gas flow is obtained from the saturation vapor pressure of the anesthetic and the split ratio of the bypass gas flow to the evaporator chamber gas flow.
The dispensing element downstream of the evaporator chamber is designed as a cone in a conical sleeve, forming a cone resistance, whose degree of opening can be changed with a setting element in the form of a setting wheel. The drawback of the prior-art dispensing element is that the cone resistance requires a considerable manufacturing effort, must be manufactured with high precision and must be guided with very high precision in order to obtain the desired scaling over an angle range of up to 300° in terms of the angle of rotation for the anesthetic concentration on the setting wheel.
An evaporation device for volatile anesthetics (anesthetic vaporizer), in which the anesthetic dispensing is carried out by means of manually rotatable dispensing plates and a ring groove, is known from DE-AS 18 11 817.
Such dispensing grooves must be manufactured with very high precision in order to meet the very high requirement on the accuracy of setting for the anesthetic concentration in case of small anesthetic vapor volumes, i.e., a low concentration setting. Furthermore, the scaling of the concentration marks that can be obtained with these dispensing grooves on the setting wheel with only a small angle of up to about 120° between the off position and the maximum concentration mark is disadvantageous. This leads to reduced precision of setting compared to the conical dispensing elements.